17,102 research outputs found
The formation of spiral arms and rings in barred galaxies
In this and in a previous paper (Romero-Gomez et al. 2006) we propose a
theory to explain the formation of both spirals and rings in barred galaxies
using a common dynamical framework. It is based on the orbital motion driven by
the unstable equilibrium points of the rotating bar potential. Thus, spirals,
rings and pseudo-rings are related to the invariant manifolds associated to the
periodic orbits around these equilibrium points. We examine the parameter space
of three barred galaxy models and discuss the formation of the different
morphological structures according to the properties of the bar model. We also
study the influence of the shape of the rotation curve in the outer parts, by
making families of models with rising, flat, or falling rotation curves in the
outer parts. The differences between spiral and ringed structures arise from
differences in the dynamical parameters of the host galaxies. The results
presented here will be discussed and compared with observations in a
forthcoming paper.Comment: 16 pages, 13 figures, accepted in A&A. High resolution version
available at http://www.oamp.fr/dynamique/pap/merce.htm
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How Stigma Impacts the Utilization of Mental Health Services Among Young Adults\u27 Within Three Different Ethnic Minority Communities
Mental health is an important aspect of every individual’s life. However, regardless of its importance, mental health is a topic that does not get much recognition. It is often simply brushed under the rug and ignored. Consequently, individuals who have mental health diagnoses may or may not choose to seek the necessary assistance. This specifically seems to be the case among adolescents and young adults within various ethnic communities, which may be due to the stigma surrounding mental health in their communities. To illustrate, regardless of the high prevalence rate of mental health issues among the minority youth, many of them still do not utilize the appropriate mental health services. With all that being said, this study questions how stigma influences the utilization of mental health services among young adults’ within the Latino/Latinx, African American, and Asian American communities through the descriptive, secondary data analysis of the UCLA Center for Health Policy Research 2021 California Health Interview Survey (CHIS) data. The key hypothesis for this study was that a major factor on whether or not these young adults’ speak out and seek help in regards to their mental health is the stigma that their race and ethnicity face. Descriptive analysis was utilized to identify frequencies of variables, quantitative analysis techniques were used to analyze the additional CHIS data, and a multiple logistic regression was conducted in order to identify any significant relationships between the variables. The findings of this research study indicate that stigma associated with mental health may not be the only factor in determining young adults’ utilization of mental health services
On the origin of rR_1 ring structures in barred galaxies
We propose a new theory for the formation of rR_1 ring structures, i.e. for
ring structures with both an inner and an outer ring, the latter having the
form of ``8''. We propose that these rings are formed by material from the
stable and unstable invariant manifolds associated with the Lyapunov orbits
around the equilibrium points of a barred galaxy. We discuss the shape and
velocity structure of the rings thus formed and argue that they are in
agreement with the observed properties of rR_1 structures.Comment: 8 pages, 9 figures, accepted in Astronomy and Astrophysics. High
quality figures are available upon reques
Invariant manifolds as building blocks for the formation of spiral arms and rings in barred galaxies
We propose a theory to explain the formation of spiral arms and of all types
of outer rings in barred galaxies, extending and applying the technique used in
celestial mechanics to compute transfer orbits. Thus, our theory is based on
the chaotic orbital motion driven by the invariant manifolds associated to the
periodic orbits around the hyperbolic equilibrium points. In particular, spiral
arms and outer rings are related to the presence of heteroclinic or homoclinic
orbits. Thus, R1 rings are associated to the presence of heteroclinic orbits,
while R1R2 rings are associated to the presence of homoclinic orbits. Spiral
arms and R2 rings, however, appear when there exist neither heteroclinic nor
homoclinic orbits. We examine the parameter space of three realistic, yet
simple, barred galaxy models and discuss the formation of the different
morphologies according to the properties of the galaxy model. The different
morphologies arise from differences in the dynamical parameters of the galaxy.Comment: 8 pages, 4 figures, in the proceedings of the conference: "Chaos in
Astronomy", Athens, September 2007, G. Contopoulos and P.A. Patsis (eds), to
be published by Springe
L1CAM binds ErbB receptors through Ig-like domains coupling cell adhesion and neuregulin signalling.
During nervous system development different cell-to-cell communication mechanisms operate in parallel guiding migrating neurons and growing axons to generate complex arrays of neural circuits. How such a system works in coordination is not well understood. Cross-regulatory interactions between different signalling pathways and redundancy between them can increase precision and fidelity of guidance systems. Immunoglobulin superfamily proteins of the NCAM and L1 families couple specific substrate recognition and cell adhesion with the activation of receptor tyrosine kinases. Thus it has been shown that L1CAM-mediated cell adhesion promotes the activation of the EGFR (erbB1) from Drosophila to humans. Here we explore the specificity of the molecular interaction between L1CAM and the erbB receptor family. We show that L1CAM binds physically erbB receptors in both heterologous systems and the mammalian developing brain. Different Ig-like domains located in the extracellular part of L1CAM can support this interaction. Interestingly, binding of L1CAM to erbB enhances its response to neuregulins. During development this may synergize with the activation of erbB receptors through L1CAM homophilic interactions, conferring diffusible neuregulins specificity for cells or axons that interact with the substrate through L1CAM
Coherent two pion photoproduction on 12C
We develop the formalism for coherent two pion photoproduction in nuclei and
perform actual calculations of cross sections for and
photoproduction on . We find that due to the isospin symmetry the cross
section for production is very small and has a maximum when the
pions propagate together. However, the kinematical region where the energies
and polar angles of the two mesons are equal and their relative
azimuthal angle is forbidden. Conversely in the
production the pions prefer to have a relative azimuthal angle 180 and the
production of the pions propagating together is suppressed. The dominant
one-body mechanism in both channels is related to the excitation of the
isobar. Hence the reaction can serve as a source of information about
's properties in nucleus. We have found that the reaction is sensitive
to effects of the pion and renormalization in the nuclear medium,
similar to those found in the coherent reaction, but magnified
because of the presence of the two pions.Comment: 17 pages LATEX and 11 postscript figure
Inhibition of Nuclear Factor of Activated T-Cells (NFAT) Suppresses Accelerated Atherosclerosis in Diabetic Mice
OBJECTIVE OF THE STUDY: Diabetic patients have a much more widespread and aggressive form of atherosclerosis and therefore, higher risk for myocardial infarction, peripheral vascular disease and stroke, but the molecular mechanisms leading to accelerated damage are still unclear. Recently, we showed that hyperglycemia activates the transcription factor NFAT in the arterial wall, inducing the expression of the pro-atherosclerotic protein osteopontin. Here we investigate whether NFAT activation may be a link between diabetes and atherogenesis. METHODOLOGY AND PRINCIPAL FINDINGS: Streptozotocin (STZ)-induced diabetes in apolipoprotein E(-/-) mice resulted in 2.2 fold increased aortic atherosclerosis and enhanced pro-inflammatory burden, as evidenced by elevated blood monocytes, endothelial activation- and inflammatory markers in aorta, and pro-inflammatory cytokines in plasma. In vivo treatment with the NFAT blocker A-285222 for 4 weeks completely inhibited the diabetes-induced aggravation of atherosclerosis, having no effect in non-diabetic mice. STZ-treated mice exhibited hyperglycemia and higher plasma cholesterol and triglycerides, but these were unaffected by A-285222. NFAT-dependent transcriptional activity was examined in aorta, spleen, thymus, brain, heart, liver and kidney, but only augmented in the aorta of diabetic mice. A-285222 completely blocked this diabetes-driven NFAT activation, but had no impact on the other organs or on splenocyte proliferation or cytokine secretion, ruling out systemic immunosuppression as the mechanism behind reduced atherosclerosis. Instead, NFAT inhibition effectively reduced IL-6, osteopontin, monocyte chemotactic protein 1, intercellular adhesion molecule 1, CD68 and tissue factor expression in the arterial wall and lowered plasma IL-6 in diabetic mice. CONCLUSIONS: Targeting NFAT signaling may be a novel and attractive approach for the treatment of diabetic macrovascular complications
Sexual dimorphisms in leukocyte trafficking in a mouse peritonitis model
E.K was funded by the British Heart Foundation Grant # FS113028789 and JRW was funded by Arthritis Research-UK Grant #19207
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